nemaline myopathy 5C

Nemaline myopathy 5C (NEM5C) is a relatively mild skeletal muscle disorder with wide clinical variability, even within families [1][2][3]. It is characterized by the presence of rods or nemaline bodies in myofibers detected by modified Gomori trichrome technique [8].

The condition can range from severe perinatal muscle weakness to milder childhood-onset forms [9]. Affected individuals may experience muscle weakness, feeding and swallowing difficulties, and joint deformities [6]. The clinical presentation of NEM5C is diverse, making it challenging to diagnose and manage.

Nemaline myopathy 5C is inherited in an autosomal dominant pattern, meaning a single copy of the mutated gene is sufficient to cause the condition. The TNNT1 gene on chromosome 19 is responsible for this form of nemaline myopathy [4].

It's essential to note that NEM5C is a relatively mild form of nemaline myopathy compared to other forms, such as Nemaline Myopathy (NM) which is characterized by congenital onset bulbar and extremity weakness and hypotonia [5].

Nemaline myopathy 5C is a rare neuromuscular condition characterized by muscle weakness, particularly in the muscles of the face, neck, trunk, and proximal limbs [4]. The clinical features of this condition include:

• Muscle weakness (myopathy) throughout the body, with severe involvement of the facial, neck, trunk, and proximal limb muscles [4]
• Difficulty walking on the heels, waddling gait, and proximal muscle weakness affecting both upper and lower limbs [2-3]
• Gowers sign, which is a characteristic feature of nemaline myopathy [2-3]

Additional symptoms may include:

• Hypotonia (decreased muscle tone)
• Muscle contractures
• Difficulty climbing stairs, running, or walking

It's worth noting that the severity and progression of these symptoms can vary widely among individuals with nemaline myopathy 5C.

References: [2] Features include difficulty walking on the heels, waddling gait, proximal muscle weakness affecting the upper and lower limbs, and Gowers sign. Additional features may include hypotonia. [3] Features include difficulty walking on the heels, waddling gait, proximal muscle weakness affecting the upper and lower limbs, and Gowers sign. Additional features may include hypotonia. [4] People with nemaline myopathy have muscle weakness (myopathy) throughout the body, but it is typically most severe in the muscles of the face; neck; trunk; and proximal limb muscles.

Diagnostic Tests for Nemaline Myopathy 5C

Nemaline myopathy 5C, a rare genetic disorder, can be challenging to diagnose. However, several diagnostic tests have been established to confirm the condition.

• Muscle Biopsy: A muscle biopsy is a surgical procedure that involves removing a small sample of muscle tissue for examination under a microscope. This test has been used to establish the diagnosis of nemaline myopathy in 49 out of 50 cases [1]. The presence of nemaline bodies, which are characteristic rod-shaped structures within muscle fibers, can confirm the condition.
• Genetic Testing: Genetic testing involves analyzing DNA samples from an individual or their family members to identify specific genetic mutations associated with nemaline myopathy. A multigene panel test has been used to identify genetic mutations in individuals who pursued genetic testing [2].
• Electrophysiological Studies: Electrophysiological studies, including nerve conduction studies and electromyography (EMG), can help assess muscle function and detect abnormalities associated with nemaline myopathy.
• Imaging Studies: Imaging studies, such as magnetic resonance imaging (MRI) or computed tomography (CT) scans, may be used to rule out other conditions that cause similar symptoms.

It is essential to consult a medical professional for accurate diagnosis and treatment of nemaline myopathy 5C. They will determine the best course of action based on individual circumstances.

References:

[1] K Amburgey · 2021 · Cited by 29 — The diagnosis of NM was established by muscle biopsy in 49 of 50 cases. [2] K Amburgey · 2021 · Cited by 29 — All individuals who pursued genetic testing had, at minimum, a multigene panel test.

Current Status of Drug Treatment for Nemaline Myopathy 5C

Nemaline Myopathy 5C (NEM5C) is a relatively mild skeletal muscle disorder with wide clinical variability, even within families [4]. Unfortunately, there are currently no approved treatments available to treat the muscle weakness associated with nemaline myopathy, including NEM5C.

Research and Potential Therapies

However, research has been conducted on potential therapies for nemaline myopathy. A study published in 2021 tested the ability of tirasemtiv, a fast skeletal troponin activator, to improve muscle function in nemaline myopathy [2]. Another study from 2023 found that inhibiting myostatin can mitigate muscle deficits in nebulin-based typical nemaline myopathy, potentially serving as a therapeutic strategy [3].

Current Research and Future Directions

While these studies provide promising leads for potential therapies, no specific treatment has been approved to date. Further research is needed to develop effective treatments for NEM5C and other forms of nemaline myopathy.

References:

[1] by J Lindqvist · 2023 · Cited by 2 — Currently, there are no approved treatments available for nemaline myopathy. [2] by JM de Winter · 2021 · Cited by 15 — To date, no specific therapy is available to treat muscle weakness in nemaline myopathy. [3] by J Lindqvist · 2023 · Cited by 2 — These findings indicate that inhibiting myostatin can mitigate muscle deficits in nebulin-based typical nemaline myopathy, potentially serving as a therapeutic strategy. [4] Autosomal dominant nemaline myopathy-5C (NEM5C) is a relatively mild skeletal muscle disorder with wide clinical variability, even within families.

Nemaline myopathy 5C (NEM5C) is a relatively mild skeletal muscle disorder, and its differential diagnosis can be complex due to its wide clinical variability. However, based on the available information, here are some conditions that may be considered in the differential diagnosis of NEM5C:

• Other forms of nemaline myopathy: NEM5C is one of several subtypes of nemaline myopathy, and other forms such as NEM1A, NEM2B, and NEM3 should also be considered in the differential diagnosis.
• Muscular dystrophies: Conditions like Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) can present with similar symptoms to NEM5C, including muscle weakness and wasting.
• Myotonic dystrophy: This is a genetic disorder that affects muscle tone and can cause muscle stiffness, weakness, and wasting. Some cases of myotonic dystrophy may be misdiagnosed as nemaline myopathy.
• Congenital muscular dystrophies: Conditions like congenital muscular dystrophy (CMD) and Bethlem myopathy can present with similar symptoms to NEM5C, including muscle weakness and joint contractures.
• Other neuromuscular disorders: Conditions like spinal muscular atrophy (SMA), Charcot-Marie-Tooth disease (CMT), and facioscapulohumeral muscular dystrophy (FSHD) may also be considered in the differential diagnosis of NEM5C.

It's worth noting that a definitive diagnosis of NEM5C typically requires genetic testing to confirm the presence of pathogenic variants in the ACTA1, NEB, or TPM2 genes. A thorough clinical evaluation and muscle biopsy can also provide important diagnostic information.

References:

• [3] Nemaline myopathy is a congenital neuromuscular disorder affecting skeletal muscles, leading to muscle weakness, feeding and swallowing difficulties, and joint contractures.
• [4] The clinical presentation of affected individuals ranges from severe perinatal muscle weakness to milder childhood-onset forms, and the disease severity can vary widely among patients.
• [8] Nemaline myopathy: a clinical study of 143 cases. This study highlights the importance of considering other neuromuscular disorders in the differential diagnosis of nemaline myopathy.
• [9] Most NEB-NM patients have autosomal recessive disease due to a compound heterozygous genotype, which can be an important factor in the differential diagnosis of NEM5C.